1. Field of the Invention
The present invention broadly relates to furniture designed for shelf storage of both hard and soft goods of varying weight. In particular, this invention focuses on furniture incorporating flexible panels tensilely stressed as structural elements for the purpose of creating lightweight storage furniture that dramatically improves strength-to-weight performance ratios while reducing the cost of manufacture and distribution.
2. Prior Art
There is abundant history of the use of fabric panels as structural elements in casual furniture, including items like hammocks, director's chairs, and pool-deck chaise lounges that demonstrate the considerable strength of fabric panels. Being designed to support humans, the fabric panels of this type of furniture are largely unstressed in order to provide a gradual curved, comfortable support surface. This is traditionally accomplished by suspending either somewhat elastic material or slackened inelastic material between rigid support members. While practical for supporting an individual, this kind of support surface is inappropriate for the organized storage of multiple items, animate or inanimate, because unstressed panels have the inherent problem of panel sag under loading conditions when objects tend to slip towards the center. This slippage causes congestion, inefficient weight distribution and compromised capacity.
Efforts to create a more planar-like storage surface with flexible panels has had mixed results. Much of the prior art resorts to some form of rigid insert in combination with one or more fabric panels, as typified by U.S. Pat. No. 3,519,318, which describes "flat shelf boards co-extensive with and supported by the cross canvas strips." Although rigidity can be achieved in this manner, the practice tends to be undesirable for two reasons: 1) the cost-ineffectiveness of including two components that separately could each perform the storage surface function and 2) the extra weight burden of any unnecessary stiffening material.
In a different approach, Erikson et al. teach in U.S. Pat. No. 4,270,816 that deflection of the fabric plane can be minimized by tensilely stressing the fabric panel in one direction. However, actual usage based on this prior art reveals two inherent problems. First, stressing panels in only one direction severely compromises the fabric's overall tensile strength capacity. In the typical cross-weave fabric as illustrated in U.S. Pat. No. 4,270, 816, fibers in the stressed direction are directly burdened with dynamic loads, while the remaining perpendicular fibers carry little of the load stress. Even with non-woven fabrics, tensile strength capacity is significantly underutilized. As a result, the one-way stressed fabric panels experience significant deflection under everything but light dynamic loads unless rigid inserts are incorporated. Indeed, Erikson et al. admit "additional rods may be provided beneath the shelves for support or to lend structural rigidity." The second inherent problem concerns prestressing the fabric panels by a single, pre-determined dimension with no apparent means of adjusting the level of tensile stress to properly accommodate varying load factors or residual elasticity upon subsequent load applications.